Part Throttle Hesitation -> WOT Bucking

[m1k3]

I'm having problems with partial throttle. Full throttle seems to be ok but at part throttle (40%) when building boost the car hesitates and surges a little around 3500. If I shift at 4500 and punch it at 3000, it will climb to 4500 hesitate and buck and then take off. I datalogged it and it isn't linked with knock, but my TPS only read about 85-89% throttle. I recently replaced my ISC due to idle surge, new plugs gapped .28, intercooler leak fixed.

My ideas are

Wires (look good)
O2 Sensor
TPS

Anyone have similar problems?

 

[Mitsuturbo]

This is kind of a "duh", i know.... but many people seem to not associate an un-plumbed BOV with this problem... If your BOV is vented to atmosphere without a VPC or something similar in the works, then your MAF and Injectors don't agree when your BOV is venting some some pressure due to more pressure in the intake tract than in the manifold.. causing less pressure to hold DOWN your BOV and allowing it to open at part throttle.. sometimes at full throttle as low as 14 psi from what i have seen.

If your BOV is plumbed back into the intake.... disregard, i suppose.

Hope that's your problem, as i have seen it many times, and it's an easy fix.
However, seeing that you have a logger, etc, i'm guessing this is NOT your problem... just thought i would mention it, "just in case".

I do not know how knowledgeable you are about DSM's so please dont be insulted by this "duh" diagnosis.

 

[m1k3]

Thanks for the reply but I'm not venting. I'm going to check for boost leaks today and see what's going on.

 

[m1k3]

Found two new leaks tonight, the vacuum hose for the BOV was cracked and the UICP was leaking at the throttlebody elbow. Fixed those two and there is still one on the throttlebody where the throttle cable is connected to the throttle plate. It's right under that metal coil (shaft seals leaking?). Plus a few small ones around the gasket. Soap and water does the trick. Get back to you tomorrow whether this has fixed anything or not.